I'm very sorry to hear about your chicks.
Could you post a few pictures or a video, of the chicks affected? How old are they? Are they exhibiting signs of heavy breathing, or nasal discharge? Have you checked inside their mouth for any lesions? Do you have any photos of their poop?
Judging from the symptoms you describe, it's possible they have a respiratory infection. Respiratory diseases such as Mycoplasma Galliseptcum, or Coryza, can cause facial edema, and depending on the strain, can have high mortality rates in chicks. Coryza often produces thick cheesy-like, bad-smelling lesions inside the mouth.
There is no treatment for these viruses only antimicrobial therapy, and supportive care. Tylosin, doxycycline, or Baytril can be purchased online for MG, for Coryza, a sulfa drug would be best used. Birds affected with MG and Coryza will remain carriers for life, and overtime a new antibiotic may need to be chosen. You can have testing done by your state lab, or a national lab to determine the nature of which virus you're dealing with.
In addition to antimicrobial therapy, providing the birds with vitamins, especially zinc which supports immune response to viruses may prove useful, as would decreasing ammonia in their pen, reducing dust, and increasing ventilation.
https://www.metzerfarms.com/PoultryLabs.cfm
https://zoologix.com/avian/index.htm